Interrogation units for transponder systems typically use amplitude modulation to transfer data from the interrogation unit to the transponder. Amplitude modulation requires high quality resonators at both the transponder and the interrogation units in order to achieve long read/write distances between the transponder and interrogator units. High quality factor resonators have long build up times, thus leading to slow data transmission rates. Further, maximum data transmission rates differ according to different quality factors of the resonator circuits at the transponder and interrogation units. Also, maximum data transmission rates differ according to the distance between the interrogation unit and the transponder unit. Therefore, it is desirable to increase the data transmission speed between an interrogation unit and a transponder unit while maintaining long read/write distances.